The provision of one or more stops in a rotatable connection or a pivot connection for limiting or defining a range of rotational movement available in a support arm or mounting arm or other structure is known in the art. Conventionally, however, such stops are fixed and do not enable the user to adjust or modify the range of movement depending upon the particular spatial parameters available for the installation of the rotatable connection and/or depending upon the technical field of application. Thus, the present invention is directed to the problem of providing a new and improved stop mechanism for a rotatable joint, with which a user may readily adjust and/or set a range of rotational movement in the joint.